Paper and polyethylene insulated electrical wire may suffer from degradation of its protective covering. This degradation can result in failure of the electrical properties of the wire or cause it to short out. A further problem exists with spiral wrapped paper insulation. Splicing and other handling of the wire tends to result in exposure of the copper core. Particularly, such handling can cause unravelling of the spiral wrapped paper insulation. To overcome this problem without expensive rewiring, field applied spray insulation has been developed. An aliphatic polyurethane system useful as a field-applied spray insulation (i.e., B-Insulation Spray, Sprayon Products Div. of Sherwin-Williams Co.) was disclosed by J. W. Shea at the Proceedings of the 21st International Wire and Cable Symposium, Cherry Hill, NJ, "Treatment of Degraded PIC Insulation in Pedestal Closures Associated with Buried Plant," pp. 70-74, 1971. This system has utility for polyethylene insulated wires, but has not been found to be useful on paper.
Ethylene resins useful as coating compositions are known. For example, U.S. Pat. No. 4,237,037 discloses a hot melt powder composition for coating metallic substrates comprising an ethylene resin mixture composed of an ethylene copolymer and a graft copolymer of polyethylene and a hydrocarbon wax.
A moldable thermoplastic composition containing a minor amount of an esterified olefin-maleic anhydride copolymer is disclosed in U.S. Pat. No. 4,192,930.
Japanese Patent application No. 78-038 (1980) (Derwent Abstract available) teaches olefinic polymers and copolymers with cyclo-olefin and maleic anhydride for bonding to metals when the polymeric composition is in the molten state.
It is novel in the art to provide a sprayable field-applied insulation which is a solvent-containing mixture comprising an anhydride copolymer, a flexibilizing polymer, and a fluorochemical compound, the mixture being inexpensive, easily applied, having good electrical characteristics, drying rapidly, resisting moisture, thermally stable at pedestal temperatures, non-flammable, having good clarity so color coding is not affected, and having no effect on connectors and other hardware normally used in wire splicing and terminating, and useful for pulp, polyethylene, and paper insulated wires.